The present disclosure relates generally to perpendicular magnetic recording (PMR) systems for hard disk drives, and more particularly, to PMR write heads.
Hard disk drives are used to store and retrieve digital information for computers and other devices. A typical hard disk drive includes a high speed rotating disk having a magnetic material on its surface. Digital information is written to and read from the disk as it rotates past a magnetic head over an air bearing interface. The magnetic head is used to detect and modify the magnetic polarization of the disk's surface immediately below it. An actuator arm moves the magnetic head on an arc across the rotating disk, thereby allowing the magnetic head to access the entire disk.
The disk includes multiple concentric tracks that cover the disk's surface. The magnetic head writes data to the disk by magnetizing segments along the circular tracks of the rotating disk. Each segment represents one bit of information. The storage capacity of a hard disk drive is a function of how large a segment must be to represent one bit of information. The capacity is often measured in terms of areal density. Areal density is equal to the bits-per-inch along the track times the tracks-per-inch radially on the disk.
In older hard disk drive designs, the bits were oriented circumferentially along the track and parallel to the disk. Today, in most hard disk drives, the bits are orientated perpendicular to the disk. These systems, known as PMR systems, reduce the size of the segment required to represent one bit of information through the perpendicular orientation of the magnetization, thereby increasing the areal density.
The magnetic head for a PMR system is designed to generate a perpendicular magnetic field. This may be achieved by embedding a soft magnetic under-layer into the disk, below the magnetic surface. In this configuration, the magnetic flux, which results from the magnetic field produced by the magnetic head, is collected by the soft magnetic under-layer and returned to the magnetic head to complete the magnetic circuit. The result is a magnetic charge with a perpendicular orientation in the surface of the disk.
As consumer demand for improved areal density increases for PMR systems, it may be desirable to implement new PMR head designs with smaller write pole tip geometry at air bearing surface (ABS) while maintaining sufficient magnetic fields.